I Have Been trying to build or find an inexpensive way to convert a 0-12 volt input to a 4-20ma output to toggle a low volt warning for a solar powered device, It needs to be low power draw and small in size A programmable 1B22 voltage to current converter looks to be out of my price range right now... any ideas would be wonderful...

 

I've used the XTR115 in several designs, with good results. It lists on Digi-Key for ≈$3.50 in single quantities; I don't know if that's out of your price range or not, since you didn't specify.

 

hi,
This is one option, use OPA's that tolerate close to supply voltage inputs.
E

 

I've used the XTR115 in several designs, with good results. It lists on Digi-Key for ≈$3.50 in single quantities; I don't know if that's out of your price range or not, since you didn't specify.

Looks like It Might Be a good Option for me, I am just not real good with schematics, Would I be able to use this as a 3 or 4 connection option, 12v + input and a single 4-20 output... I have not used OPA's I/C's with out detailed instructions, Thanks

 

Looks like It Might Be a good Option for me, I am just not real good with schematics, Would I be able to use this as a 3 or 4 connection option, 12v + input and a single 4-20 output... I have not used OPA's I/C's with out detailed instructions, Thanks

The XTR115 is not an op amp; it's a special-purpose IC for making loop-powered 4-20 mA devices. It's worth the time to read the data sheet, as it gives you all you need to know to use it.

 

The XTR115 is not an op amp; it's a special-purpose IC for making loop-powered 4-20 mA devices. It's worth the time to read the data sheet, as it gives you all you need to know to use it.

Sorry but I believe the most difficult for the OP would be how to bring the 0-12 V variation within the valid input range to the IC.

My real concern at least.

 

Sorry but I believe the most difficult for the OP would be how to bring the 0-12 V variation within the valid input range to the IC.

The control input to the IC is a current, not a voltage; all that's needed is to calculate the appropriate value resistor for the desired input voltage range. For an offset input, which is what the TS needs (0-12V gives 4-20 mA), see the "Offsetting the Input" section in the datasheet, Figure 2 on page 6.

 

The control input to the IC is a current, not a voltage; all that's needed is to calculate the appropriate value resistor for the desired input voltage range. For an offset input, which is what the TS needs (0-12V gives 4-20 mA), see the "Offsetting the Input" section in the datasheet, Figure 2 on page 6.

That reminds me the CA 3080.

 

For what it's worth, the circuit he needs is in Fig. 2, with an input resistor of 75 kΩ and Ro = 62.5 kΩ.